U.S. patent number 4,941,482 [Application Number 07/225,693] was granted by the patent office on 1990-07-17 for apparatus for measuring the density of a tobacco stream.
This patent grant is currently assigned to Korber AG. Invention is credited to Uwe Heitmann, Heinz-Christen Lorenzen, Peter Pinck, Wolfgang Siems.
United States Patent |
4,941,482 |
Heitmann , et al. |
* July 17, 1990 |
Apparatus for measuring the density of a tobacco stream
Abstract
The density of a tobacco stream which is advanced by a
foraminous conveyor toward the surplus removing station of a
cigarette rod making machine is measured by one or more detectors
each having one or more sources of infrared light and one or more
photoelectric transducers. In order to avoid the generation of
distorted signals in response to impingement of high-intensity
radiation upon the transducer or transducers, each transducer is
out of line with the path of direct propagation of radiation from
the respective source or sources toward successive increments of
the tobacco stream. The transducer or transducers receive infrared
light which is scattered in and/or reflected by tobacco particles
in the stream. Signals from the transducer or transducers are used
to regulate the quantity of surplus which is removed from the
stream.
Inventors: |
Heitmann; Uwe (Hamburg,
DE), Lorenzen; Heinz-Christen (Wentorf,
DE), Siems; Wolfgang (Hamburg, DE), Pinck;
Peter (Gross-Hansdorf, DE) |
Assignee: |
Korber AG (Hamburg,
DE)
|
[*] Notice: |
The portion of the term of this patent
subsequent to February 21, 2006 has been disclaimed. |
Family
ID: |
6332765 |
Appl.
No.: |
07/225,693 |
Filed: |
July 28, 1988 |
Foreign Application Priority Data
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Jul 31, 1987 [DE] |
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3725366 |
|
Current U.S.
Class: |
131/84.4;
131/905; 131/906 |
Current CPC
Class: |
A24C
5/1871 (20130101); A24C 5/3412 (20130101); G01N
21/85 (20130101); G01N 21/3563 (20130101); G01N
21/35 (20130101); Y10S 131/905 (20130101); Y10S
131/906 (20130101) |
Current International
Class: |
A24C
5/34 (20060101); A24C 5/18 (20060101); A24C
5/32 (20060101); A24C 5/00 (20060101); G01N
21/85 (20060101); G01N 21/35 (20060101); G01N
21/31 (20060101); A24C 005/14 () |
Field of
Search: |
;131/84.4,905,906,908,907 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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759532 |
|
Oct 1958 |
|
GB |
|
1128003 |
|
Sep 1968 |
|
GB |
|
Primary Examiner: Millin; V.
Assistant Examiner: Crosby; D. F.
Attorney, Agent or Firm: Kontler; Peter K.
Claims
We claim:
1. A method of measuring the density of an unwrapped tobacco stream
in a rod making machine, comprising the steps of advancing the
stream by a radiation-permeable conveyor along a first path;
directing against the stream at least one beam of radiation along a
second path adjacent a predetermined portion of said first path so
that radiation which propagates itself along the second path
penetrates into and through the stream and through the conveyor and
that radiation which penetrates through successive increments of
the stream is indicative of the density of the respective
increments; and measuring the intensity of radiation which
penetrates through and issues from the conveyor.
2. Apparatus for measuring the density of an unwrapped tobacco
stream in a rod making machine, comprising means for advancing the
stream in a predetermined direction; a first component including at
least one radiation source arranged to direct radiation against the
stream along a predetermined path whereby the extent of penetration
of radiation through the stream is indicative of density of the
stream; a second component including at least one radiation
receiver positioned to receive radiation which penetrates through
and issues from the stream, said radiation receiver being spaced
apart from said path; a third component including at least one
radiation source arranged to direct radiation against the stream
along a second predetermined path whereby the extent of penetration
of such radiation through the stream is indicative of density of
the stream; and a fourth component including at least one radiation
receiver arranged to receive radiation which issues from the source
of said third component and penetrates through the stream, the
radiation receiver of said fourth component being spaced apart from
said second path and said third and fourth components being located
upstream of said first and second components so that radiation
issuing from the source of said first component penetrates through
successive increments of the advancing stream after such increments
advance into and beyond the range of the source of said third
component.
3. Apparatus for measuring the density of an unwrapped tobacco
stream in a rod making machine wherein the rod making machine
comprises means for advancing the stream including a foraminous
conveyor disposed at a level above the stream, said apparatus
comprising a first component including at least one radiation
source arranged to direct radiation against the stream along a
predetermined path whereby the extent of penetration of radiation
through the stream is indicative of density of the stream; and the
second component including at least one radiation receiver
positioned to receive radiation which penetrates through and issues
from the stream, said radiation receiver being spaced apart from
said path and one of said components being disposed above the
conveyor so that radiation between the stream and said one
component passes through the conveyor.
4. Apparatus for measuring the density of an unwrapped tobacco
stream in a rod making machine wherein the rod making machine
comprises a tobacco channel and means for advancing the stream in
the channel, said apparatus comprising a first component adjacent
the tobacco channel and including at least one radiation source
arranged to direct radiation against the stream along a
predetermined path whereby the extent of penetration of radiation
through the stream is indicative of density of the stream; a second
component including at least one radiation receiver adjacent the
tobacco channel and positioned to receive radiation which
penetrates through and issues from the stream, said radiation
receiver being spaced apart from said path and including means for
generating first signals having characteristics which are
indicative of the intensity of radiation that has passed through
the stream and reaches said receiver, the tobacco channel of the
rod making machine having wall means provided with a window for
radiation between the stream in the tobacco channel and one of said
components, said window being positioned to transmit a portion of
radiation which is influenced by tobacco at the level of the window
and at a level below the window; means for evaluating said signals;
and means for monitoring the density of successive increments of
the stream in a substantially vertical plane including means for
generating second signals denoting the density of successive
increments of the stream in said plane and for transmitting said
second signals to said evaluating means to influence said first
signals.
Description
BACKGROUND OF THE INVENTION
The invention relates to improvements in apparatus for measuring
the density of a tobacco stream, especially in a rod making
machine. More particularly, the invention relates to improvements
in apparatus which measure the density of successive increments of
an advancing tobacco stream by causing one or more beams of
radiation to penetrate into the stream and by ascertaining the
characteristics (such as the intensity) of radiation which
penetrates through the stream.
It is known to measure the density of a tobacco stream with a
detector wherein a source of beta rays, visible rays or infrared
rays directs one or more beams of radiation against the stream and
a suitable transducer serves to generate signals which are
indicative of the characteristics of that portion of each beam
which has penetrated through the stream. Reference may be had, for
example, to commonly owned copending patent applications Ser. Nos.
760,995 and 837,096 of Radzio et al. A drawback of presently known
density measuring apparatus of the above outlined character is that
the results of measurements are not reliable under any and all
circumstances which are likely to be encountered in connection with
the density measurement of a tobacco stream in a cigarette rod
making or like machine. For example, if the stream exhibits
pronounced hills and valleys, the intensity of radiation which
penetrates through the stream is likely to reach a value which
affects the accuracy of signals from the transducer of the
detector. Thus, if the beam of radiation issuing from a source
passes through the tobacco stream in a region where the stream
exhibits a pronounced depression or valley, the intensity of
radiation to which the transducer is exposed can reach a value
which entails a distortion of the signal from the transducer to the
evaluating circuit so that the signal is not truly indicative of
actual density of the respective portion of the stream. The
situation is aggravated if the stream of tobacco particles happens
to be interrupted so that the entire beam of radiation issuing from
the source impinges upon the transducer.
It was further discovered that heretofore known density measuring
apparatus do not take into consideration certain other factors
which are likely to adversely influence the accuracy of the
measurement. For example, such conventional density measuring
apparatus do not take into consideration the radiation scattering
effect of tobacco particles which are located outside of the actual
measuring or monitoring range of the detector, especially of
tobacco particles which form the surplus and must be removed in
order to convert the stream into a filler which is ready to be
draped into a web of cigarette paper or other suitable wrapping
material.
Still further, the quality of density measurement can be adversely
influenced by localized accumulations of tobacco shreds and/or by
fragments of tobacco ribs which find their way into the stream and
advance past the density measuring station close to the locus of
penetration of radiation into the stream. The transducer of the
detector is likely to transmit an inaccurate signal (i.e., a signal
which is not truly representative of the density of the
corresponding increment of the stream) if the fragments of tobacco
ribs and/or accumulations of tightly interlaced tobacco shreds
interfere with predictable penetration of radiation through the
advancing stream.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved
apparatus which can measure the density of successive increments of
an advancing tobacco stream with a degree of accuracy much higher
than that achievable with heretofore known apparatus.
Another object of the invention is to provide the apparatus with
novel and improved means for preventing the generation and
transmission of misleading signals when the stream exhibits
pronounced hills and valleys.
A further object of the invention is to provide the apparatus with
novel and improved means for preventing exposure of the signal
generating component or components to excessive radiation.
An additional object of the invention is to provide the apparatus
with novel and improved means for preventing fragments of tobacco
ribs and/or unanticipated agglomerations of tobacco shreds from
adversely influencing the measurement of density of the respective
increments of the tobacco stream.
Still another object of the invention is to provide the apparatus
with novel and improved means for compensating for the radiation
scattering effect of those portions of the tobacco stream which are
not in the immediate range of density monitoring
instrumentalities.
A further object of the invention is to provide a novel and
improved method of measuring the density of an advancing tobacco
stream in such a way that unanticipated departures of the shape
and/or density and or composition of certain increments of the
stream from anticipated values do not adversely affect the
measuring operation.
Another object of the invention is to provide a tobacco processing
machine which embodies the above outlined apparatus.
An additional object of the invention is to provide novel and
improved detector means for monitoring the density of successive
increments of a tobacco stream which is on its way to the surplus
removing station in a cigarette rod making or other tobacco
processing machine.
A further object of the invention is to provide novel and improved
tobacco guide means for use in the above outlined apparatus.
Another object of the invention is to provide the apparatus with
novel and improved means for taking into consideration all known
factors which adversely influence the measurements of density in
conventional apparatus.
An additional object of the invention is to provide an apparatus
which can be built into existing tobacco processing machines as a
superior substitute for heretofore known density measuring
apparatus.
SUMMARY OF THE INVENTION
One feature of the invention resides in the provision of an
apparatus for measuring the density of a tobacco stream in a rod
making machine. The apparatus comprises a first component including
at least one radiation source which serves to direct radiation
against the stream along a predetermined path whereby the extent of
penetration of radiation through the stream denotes the density of
the stream, and a second component including at least one radiation
receiver (e.g., a photoelectric transducer) which serves to receive
radiation that penetrates through the stream. In accordance with a
feature of the invention, the radiation receiver is spaced apart
from the path of radiation which issues from the source or sources
so that the receiver is not exposed to radiation of excessive
intensity if the tobacco stream is thinner than expected or the
beam or beams of radiation do not encounter any tobacco. It can be
said that the source or sources are disposed in a first plane and
the receiver or receivers are disposed in a different second plane.
The two planes are inclined relative to each other. This does not
prevent the source or sources and the receiver or receivers from
being located in a common plane which extends transversely of the
stream.
In accordance with a presently preferred embodiment of the improved
apparatus, the path is horizontal or substantially horizontal and
the receiver or receivers are positioned to receive radiation which
issues from the stream in a vertical or substantially vertical
direction. Alternatively, the path can be vertical or substantially
vertical, and the receiver or receivers are then positioned to
receive radiation which issues from the stream in a horizontal or
substantially horizontal direction.
The first component can include two radiation sources which serve
to direct radiation along horizontal or nearly horizontal paths,
and the means for advancing the stream can be designed to move the
stream between the sources so that the radiation penetrates into
opposite sides of the advancing stream. Alternatively, the second
component can comprise two radiation receivers and the advancing
means is then designed to move the stream between the two receivers
so that the receivers receive radiation which issues from opposite
sides of the advancing stream.
One of the first and second components can be disposed at a level
above the stream.
The advancing means can comprise a conveyor which moves the stream
in a predetermined direction. The apparatus can comprise a third
component including at least one radiation source serving to direct
radiation against the stream along a second predetermined path
whereby the extent of radiation which penetrates through the stream
is again indicative of the density of the stream, and a fourth
component including at least one radiation receiver which serves to
receive radiation issuing from the source of the third component
and penetrates through the stream. The radiation receiver of the
fourth component is spaced apart from the second path and the third
and fourth components are located upstream of the first and second
components (as considered in the direction of advancement of the
stream) so that radiation which issues from the source of the first
component penetrates through successive increments of the advancing
stream downstream of the locus of penetration of radiation which
issues from the source or sources of the third component.
The machine which embodies the improved apparatus is preferably
provided with means for forming the stream with a surplus of
tobacco and with means for removing the surplus from successive
increments of the advancing stream.
The radiation which propagates itself from the stream toward the
receiver or receivers of the second or fourth component advances
along a further path which is inclined with reference to the
corresponding predetermined path (of propagation of radiation from
the source or sources of the first or third component). The
apparatus or the machine in which the apparatus is installed
further comprises a channel for the tobacco stream, and the channel
has wall means with at least one window for radiation in one of the
paths, i.e., in the path from a source to the stram or from the
stream to a receiver. The window can include or constitute a
diaphragm which permits penetration of a predetermined amount of
radiation into the stream or issuance of radiation from a
predetermined portion of each increment of the stream. The stream
forming means is designed to deliver into the channel tobacco
particles in such quantities that the stream contains the
aforementioned surplus of tobacco, and such surplus is then removed
by the surplus removing (called trimming or equalizing) means. The
removal of surplus takes place downstream of the components of the
improved apparatus, and the machine can comprise means for moving
the surplus removing means between a plurality of levels to remove
different quantities of surplus from the stream (the stream is
normally caused to advance along a substantially horizontal path,
i.e., along a path which is inclined to the vertical). The
diaphragm is preferably located above the median level of the
surplus removing means.
The means for advancing normally comprises (or can comprise) a
foraminous conveyor which is located at a level above the stream
(the conveyor can attract the stream to its underside by suction).
One of the first and second and/or third and fourth components of
the apparatus can be installed above the conveyor so that the
radiation which propagates itself from or to such component above
the conveyor must penetrate through the conveyor on its way toward
or from the stream.
Each receiver has means for generating first signals which denote
the ascertained density of successive increments of the tobacco
stream and are transmitted to an evaluating circuit. The latter
preferably further receives second signals from a density
monitoring device which is designed to ascertain the density of
successive increments of the stream in a substantially vertical
plane The second signals influence the first signals to thus ensure
that the signal which is generated by the evaluating circuit is
truly repesentative of the density of successive increments of the
stream.
In a presently preferred embodiment of the apparatus, each source
is designed to emit infrared light.
Another feature of the invention resides in the provision of a
method of measuring the density of a tobacco stream in a rod making
machine. The method comprises the steps of advancing the stream
along a first path, directing against the stream at least one beam
of radiation along a second path adjacent a predetermined portion
of the first path so that the radiation which propagates itself
along the second path penetrates into the stream and that radiation
which penetrates through successive increments of the stream is
indicative of the density of the respective increments, and
measuring the intensity of radiation which penetrates through the
stream at a location which is out of line with the second path.
The novel features which are considered as characteristic of the
invention are set forth in particular in the appended claims. The
improved apparatus itself, however, both as to its construction and
its mode of operation, together with additional features and
advantages thereof, will be best understood upon perusal of the
following detailed description of certain presently preferred
specific embodiments with reference to the accompanying
drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary schematic partly elevational and partly
vertical sectional view of a cigarette maker embodying a density
measuring apparatus which is constructed and assembled in
accordance with the present invention;
FIG. 2 is a fragmentary transverse vertical sectional view of the
machine showing one embodiment of the density measuring apparatus
with two radiation sources at the sides of and a radiation receiver
above the tobacco stream;
FIG. 3 is a similar fragmentary transverse vertical sectional view
but showing an apparatus with a single radiation source;
FIG. 4 is a similar fragmentary transverse vertical sectional view
but showing a single radiation source at a level above and and two
receivers at opposite sides of the tobacco stream;
FIG. 5 is a view similar to that of FIG. 4 but showing an apparatus
with a single radiation receiver; and
FIG. 6 is a fragmentary plan view of a twin apparatus with the
radiation source of one unit and the radiation receiver of the
other unit disposed at one side of the tobacco stream and the
radiation receiver of the one unit and the radiation source of the
other unit disposed at the other side of the stream.
DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 shows a portion of a cigarette rod making machine wherein a
continuous tobacco stream 2 is advanced by the lower reach of an
endless foraminous belt conveyor 1 which is trained over pulleys 1a
and 1b. The conveyor 1 is driven (by at least one of the pulleys
1a, 1b) in the direction of arrow 1c and the stream 2 is formed at
the upper end of a duct 3 which serves to convey a rising shower of
tobacco particles (such as shreds of tobacco leaf laminae) toward
the underside of the lower reach of the conveyor 1 (note the arrow
3a). The lower reach of the conveyor 1 is adjacent the underside of
a suction chamber 6 which has an outlet connected to a suction
generating device 4 so as to ensure that the particles of tobacco
which form the stream 2 are attracted to and advance with the
conveyor 1 in the direction of arrow 1c. The duct 3 delivers
particles of tobacco at such a rate that the stream 2 contains a
surplus 8 of tobacco, i.e., more tobacco than is necessary to form
a continuous filler 2a which is thereupon draped into a web 9 of
cigarette paper or other suitable wrapping material. The web 9 is
drawn off a reel (not shown) and is advanced by the upper reach of
a second endless belt conveyor 11 (known as garniture) which causes
the filler 2a and the web 9 to advance through a conventional
wrapping mechanism 12 wherein the web is draped around the filler
and the filler is compressed so as to constitute the core of a
continuous cigarette rod 13. The latter is subdivided into sections
of predetermined (unit or multiple unit) length, and such sections
constitute discrete plain cigarettes or are supplied to a filter
tipping machine to be assembled with filter rod sections.
The means for removing the surplus 8 from the fully grown tobacco
stream 2 downstream of the duct 3 comprises a conventional trimming
or equalizing device 7 having one or more rotary disc-shaped
tobacco engaging and severing members 7a. The illustrated trimming
device 7 is designed to provide the filler 2a with longitudinally
spaced apart portions which contain more tobacco than the portions
between them because the filler 2a is to be converted into the core
of a cigarette rod 13 which is to yield plain cigarettes with
so-called dense ends.
The disc-shaped severing member or members 7a of the trimming
device 7 are movable up and down between a plurality of different
levels (as indicated by the arrow 18), i.e., to positions at
different distances from the lower reach of the conveyor 1, so as
to change the quantity of tobacco which forms the removed surplus
8.
The rod making machine of FIG. I further comprises a nuclear
density measuring device 14 which is located downstream of the
wrapping mechanism 12 and monitors the density of successive
increments of the core in the cigarette rod 13. The output of the
density measuring device 14 transmits signals, which denote the
density of successive increments of the condensed filler 2a, to a
control circuit 16 of known design which, in turn, transmits
signals to a servomotor 17 to move the disc-shaped member or
members 7a of the trimming device 7 up or down and to thus change
the density of the filler 2a. The monitoring device 14 and the
control circuit 16 are standard components of many rod making
machines and are manufactured and sold by the assignee of the
present application.
The rod making machine of FIG. 1 also comprises conventional means
for regulating the quantity of surplus 8 by changing the quantity
of tobacco particles in the shower within the duct 3. Such
regulating means comprises a first detector 19 upstream and a
second detector 21 downstream of the trimming station (as seen in
the direction of advancement of the stream 2). Each of the
detectors 19, 21 comprises a source of infrared radiation at one
side of the path for the stream 2 and filler 2a, and a suitable
photoelectric transducer at the other side of such path opposite
the respective radiation source. The outputs of the transducers
transmit signals which are indicative of the mass of tobacco
particles in the respective portions of the path for the stream 2
and filler 2a, and such signals are processed in a dividing circuit
22. The output of the dividing circuit 22 transmits signals to a
variable-speed motor 20 for an impeller 20a which serves as a means
for propelling particles of tobacco into the duct 3 at a rate which
is a function of rotational speed of the impeller. The signal at
the output of the circuit 22 is a quotient of signals which are
transmitted by the transducers of the detectors 19 and 21. It will
be noted that the path for the stream 2 and filler 2a is
substantially horizontal and that the radiation sources of
detectors 19, 21 emit beams of infrared light which are
substantially vertical so that the beam of infrared light which is
emitted by the radiation source of the detector 19 traverses the
entire untrimmed stream 2 downstream of the duct 3 but upstream of
the trimming station.
The improved density measuring apparatus of the rod making machine
which is shown in FIG. 1 is located upstream of the trimming device
7 and is designed to monitor primarily the density of that (upper)
portion of the stream 2 which is to form the filler 2a, i.e., which
is to advance at a level above the severing member or members 7a of
the trimming device 7. The density measuring apparatus can be
constructed in a manner as shown in FIG. 2, 3, 4, 5 or 6; its
location is indicated in FIG. 1 by a phantom-line circle A. Such
apparatus comprises at least one window or diaphragm 23 which is
located above the median level of the severing member or members 7a
beneath the lower reach of the conveyor 1. The output 24 of the
receiver or transducer of the apparatus at the locus A transmits
signals which are indicative of the density of the upper portions
of successive increments of the stream 2, and such signals are
processed by an evaluating circuit 26 which further receives
signals from the transducer of the detector 19. The evaluating
circuit 26 has an output which can transmit signals to the motor 17
to influence the level of the severing member or members 7a as a
function of monitored density of the stream 2 ahead of the trimming
station. Adjustments of the trimming device 7 in response to
signals from the evaluating circuit 26 serve to ensure that the
quantity of tobacco shreds which are permitted to bypass the
trimming device 7 is changed accordingly, i.e., that the density of
the filler 2a in the cigarette rod -3 is changed.
FIG. 2 shows the untrimmed tobacco stream 2 in a transverse
vertical sectional view. This stream is advanced in an inverted
U-shaped channel 27 having two parallel walls 27a, 27b extending
downwardly from the lower reach of the conveyor 1. The conveyor 1
constitutes the top wall of the channel 27 and each of the walls
27a, 27b is provided with a window-like diaphragm (23a, 23b) of
predetermined area which is disposed above the average or median
level of the severing member or members 7a (not shown in FIG. 2).
The apparatus of FIG. 2 comprises a first component having two
sources 28a, 28b of infrared light which direct beams of such light
along substantially horizontal paths so that infrared radiation
penetrates through the respective diaphragms 23a, 23b prior to
entering successive increments of the stream 2 in the channel 27.
The apparatus of FIG. 2 further comprises a second component
including a receiver 29 of infrared light. The receiver 29 is or
can constitute an optoelectric transducer having an output 24 which
transmits signals denoting the density of successive increments of
the stream 2 at the level of the diaphragms 23a, 23b. It will be
noted that the transducer 29 is spaced apart from the path of
propagation of radiation from the source 28a or 28b into the stream
2. This ensures that the transducer 29 is not overexposed to
infrared light, e.g., if the underside of the stream 2 in the
channel 27 is formed with highly pronounced hills and valleys so
that, were the transducer 29 located at 28b, radiation from 28a
could directly impinge upon the transducer with the result that the
signal from the output 24 of the transducer would fail to
accurately denote the monitored density of successive increments of
those portions of the stream 2 which advance at the level between
the diaphragms 23a and 23b. As can be seen in FIG. 2, radiation
which issues from the sources 28a, 28b propagates itself primarily
along horizontal paths, and radiation which issues from the stream
2 and passes through the lower reach of the conveyor 1 on its way
toward the transducer 29 advances along a substantially vertical
path. Otherwise stated, and referring to an imaginary simple
rectangular coordinate system, radiation from the sources 28a, 28b
propagates itself along the X-axis and radiation from the stream 2
toward the transducer 29 propagates itself along the Y-axis of the
coordinate system.
FIG. 3 shows a modified apparatus wherein the first component
includes a single radiation source 28 and the second component
includes a single receiver or transducer 29. The latter is again
located at a level above the lower reach of the conveyor 1 and the
stream 2. The wall 27b of the channel 27 has a window-like
diaphragm 23 for radiation which is emitted by the source 28. Such
radiation must change the direction of its propagation before it
can reach the transducer 29 because the latter is not in line with
the path of propagation of infrared light from the source 28.
In the apparatus of FIG. 4, the first component comprises a single
radiation source 28 at a level above the stream 2 in the channel
27, and the second component comprises two receivers or transducers
29a, 29b at opposite sides of the stream. These transducers receive
radiation which issues from the stream 2 and passes through the
respective diaphragms 23a, 23b in the walls 27a, 27b.
FIG. 5 shows a modification of the apparatus of FIG. 4. The first
component again comprises a single radiation source 28 at a level
above the lower reach of the conveyor 1, and the second component
comprises a single receiver or transducer 29 which receives
radiation issuing from the stream 2 and passing through a
window-like diaphragm 23 in the wall 27b of the channel 27.
The operation of apparatus which are shown in FIGS. 2 to 5 is based
on the so-called remission principle according to which the
transducer or transducers receive radiation which is reflected by
and/or scattered in successive increments of the stream 2. Such
mode of operation ensures the generation of signals having a
pronounced intensity. However, it has been found that the intensity
of signals which are generated by the transducer 29 or by the
transducers 29a, 29b are also influenced, or can be influenced, by
radiation which is scattered in the region beneath the diaphragm or
diaphragms in the wall or walls of the channel 27. Such region is
indicated at y in FIG. 4. Therefore, signals which are generated
and transmitted by the transducer or transducers of the improved
apparatus are compared in the evaluating circuit 26 of FIG. 1 with
signals from the transducer of the detector 19, i.e., from a
detector which monitors the density of the entire stream 2 ahead of
the trimming station, namely the density of the stream portion
which is to constitute the filler 2a as well as the density of the
portion 2b (FIG. 4) in the region y at a level beneath the
respective diaphragms 23a and 23b.
An advantage which is shared by each of the apparatus shown in
FIGS. 2 to 5 is that impingement of intense radiation upon the
transducer 29 or transducers 29a, 29b is prevented by the simple
expedient of installing the transducer or transducers out of line
with the direction of propagation of infrared radiation from the
source 28 or sources 28a, 28b toward the tobacco stream 2. Thus,
the accuracy of signals which are transmitted by the output or
outputs 24 of the transducer or transducers is not affected by
eventual deep valleys in the underside of the stream 2 and/or by
total absence of tobacco particles in the channel 27.
The improved apparatus can be designed in such a way that it is
also much less likely to be adversely influenced by potential
accumulations of tightly interlaced tobacco shreds and/or by the
passage of fragments of tobacco ribs past the density monitoring
station. Such accumulations of shreds and fragments of ribs could
distort the signals at the output or outputs of the transducer or
transducers, e.g., while passing very close to the locus of
penetration of radiation from one or more sources of infrared light
into the stream 2. The adverse influence of such accumulations
and/or of fragments of tobacco ribs is reliably prevented if the
improved apparatus is constructed in a manner as shown in FIG. 6.
This apparatus comprises two units A and B which may but need not
be identical and each of which can constitute an apparatus of the
type shown in FIG. 2, 3, 4 or 5. The unit B is located upstream of
the unit A, as considered in the direction of advancement of the
stream 2 in the channel including the walls 27a and 27b. For
example, the unit A can be constructed in a manner as shown in FIG.
2, and the unit B can be constructed in a manner as shown in FIG.
4. The outputs of the transducers of the units A and B transmit
signals to an averaging circuit 31 which transmits an averaged
output signal (at 24A) to the evaluating circuit 26 of FIG. 1. The
first component (radiation sources 28a, 28b) of the unit A directs
infrared light against opposite sides of the stream 2 in the
channel including the walls 27a, 27b whereas the corresponding
component (radiation sources 28) of the second unit B emits
radiation vertically downwardly so that such radiation penetrates
through the conveyor (not shown in FIG. 6) prior to entering the
stream 2.
The averaging circuit 31 takes into consideration the mutual
spacing of the units A and B, i.e., the fact that radiation which
is emitted by the source 28 of the unit B penetrates into
successive increments of the stream 2 before such increments reach
the locus of the unit A and are penetrated into by radiation
issuing from the sources 28a and 28b.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can, by applying current
knowledge, readily adapt it for various applications without
omitting features that, from the standpoint of prior art, fairly
constitute essential characteristics of the generic and specific
aspects of our contribution to the art and, therefore, such
adaptations should and are intended to be comprehended within the
meaning and range of equivalence of the appended claims.
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